Cookie leakage between different users in fastapi-proxy-lib

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Impact In the implementation of version 0.0.1, requests from different user clients are processed using a shared httpx.AsyncClient. However, one oversight is that the httpx.AsyncClient will persistently store cookies based on the set-cookie response header sent by the target server and share these cookies across different user requests. This results in a cookie leakage issue among all user clients sharing the same httpx.AsyncClient. Patches It's fixed in 0.1.0 Workarounds If you insist 0.0.1: - Do not use ForwardHttpProxy at all. - Do not use ReverseHttpProxy or ReverseWebSocketProxy for any servers that may potentially send a set-cookie response. However, it's best to upgrade to the latest version. References fixed in #10

Published by the source

1 Dec 2023, 19:23 UTC

Last modified by the source

6 Dec 2024, 05:38 UTC

Source last checked

26 Oct 2026, 13:12 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-7vwr-g6pm-9hc8

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-7vwr-g6pm-9hc8

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# Patch Next advisory brief: GHSA-7vwr-g6pm-9hc8

Advisory: Cookie leakage between different users in fastapi-proxy-lib
IDs: GHSA-7vwr-g6pm-9hc8
Record: https://patchnext.com/advisories/ghsa-7vwr-g6pm-9hc8 (revision 2, source checked 26 Oct 2026, 13:12 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: fastapi-proxy-lib 0.1.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI fastapi-proxy-lib: affected < 0.1.0; fixed in 0.1.0

## Suggested inspection (read-only)
- `python -m pip show fastapi-proxy-lib`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on fastapi-proxy-lib.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-7vwr-g6pm-9hc8 (OSV record GHSA-7vwr-g6pm-9hc8 lists affected ranges: PyPI fastapi-proxy-lib >=0 <0.1.0 (fixed))
- Verified: https://github.com/advisories/GHSA-7vwr-g6pm-9hc8 (GitHub-reviewed advisory GHSA-7vwr-g6pm-9hc8 lists affected ranges: PyPI fastapi-proxy-lib >=0 <0.1.0)

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